INTERPLANETARY SHOCK WAVE: Last night, April 19-20, a shock wave in the solar wind hit Earth's magnetic field, sparking a moderately strong G2-class geomagnetic storm and rare "electric blue" auroras seen from airplanes in flight over Canada. Northern Lights spilled across the Canadian border into a number of US states. Visit today's edition of Spaceweather.com for photos and a discussion of this unexpected event.
Above: Blue auroras photographed by pilot Matt Melnyk flying an airplane 39,000 feet over Canada on April 20th. More pictures may be found in Spaceweather.com's Realtime Aurora Gallery.
